This invention relates, in general, to a high capacity shock-absorbing apparatus and, more particularly, to an improved apparatus for frictionally absorbing shock using a helicrl gear as the primary friction cushioning element.
Prior to the instant invention, apparatus for absorbing shock, such as, draft gears used in the railroading industry, have generally consisted of a primary friction cushioning element in tandem with a secondary cushioning element, the most common being a coil spring. Other secondary cushioning elements used include rubber pads, combination coil springs and rubber cores, and complex hydraulic units. Examples of friction draft gears, which include such secondary cushioning elements, can be found in the following U.S. Pat. No. 4,296,868 (FIG. 3) shows a friction draft gear with a coil spring arrangement widely used in the industry; U.S. Pat. No. 3,178,036 (FIG. 11) also shows a friction draft gear in combination with a coil spring and rubber core that is available in the industry; U.S. Pat. No. 3,368,698 (FIG. 1) shows a hydraulic cushioning element; and U.S. Pat. No. 2,317,445 (FIG. 3) shows a rubber pad as the secondary cushioning element. All of the above references are incorporated herein by reference. The primary friction cushioning elements used prior to the instant invention with all of the above-referenced secondary cushioning elements is best shown in FIG. 1 of U.S. Pat. No. 3,368,698 and FIG. 3 of U.S. Pat. No. 4,296,868. The friction assembly shown in these references comprises an outer stationary plate in abutting relationship with the inside of the housing wall, a movable plate in abutting relationship with the outer stationary plate, an inner tapered stationary plate in abutting relationship with the movable plate, a wedge shoe in abutting relationship with the tapered stationary plate, and a center wedge to engage the wedge shoe. With this type of primary friction cushioning element, a tremendous outward force is exerted on the housing walls during closure of the draft gear assembly. This force causes the housing walls to be in almost a continuous state of flexural stress.
As is well-known, particularly in the railroad art, draft gears have two major types of loads, buff and draft. Buff loading occurs during train makeup, train operation, train braking, and "in train action" to compensate for relative movement between cars. As is taught in the prior art, a friction cushioning element buff loading causes the coupler shank to exert a compressive force that is transmitted to the follower block which, in turn, distributes the load among the center wedge and the movable plates in the draft gear. Draft loading occurs primarily during locomotive tractive actions and "in train action" to compensate for relative movement between cars. Draft loading sets up tensile forces in the coupler shank that are transmitted through the coupler key and yoke to the housing end. This force is transmitted from the housing end through the housing walls, friction clutch mechanism, and follower block that is supported by the front lugs of the draft gear pocket of the car.